The CTA on Thursday will begin a seven-month project to ease slow zones along the Purple Line north of Howard Street.

At 9 p.m. Thursday, CTA will begin the work that includes replacing 6,000 rail ties and eliminating nearly 1.3 miles of track-related slow zones.

The $2 million construction project will take place between 9 p.m. to 4:30 a.m. during the week, and from 7 a.m. to 7 p.m. on weekends.

During night work, Purple Line trains in both directions will run on a single track. Construction beginning Thursday will last until about 1:45 a.m. Friday.

During that time, southbound Purple Line trains will operate on the northbound tracks between the South Boulevard and Howard stations.

About 36 percent of the Purple Line was under slow zone last month, during which trains travel 35 miles per hour or slower. About 10,000 weekday riders boarded the Purple Line in February, the most current CTA ridership data available.